1. Field of the Invention
This present invention relates to self-sealed metal electrodes in a rechargeable oxide-ion battery (ROB) cell. More specifically, the invention describes cell component arrangement in which dense electrolyte and interconnections are used to seal a metal electrode, without introducing additional sealing components.
2. Description of Related Art
Electrical energy storage is crucial for the effective proliferation of an electrical economy and for the implementation of many renewable energy technologies. During the past two decades, the demand for the storage of electrical energy has increased significantly in the areas of portable, transportation, load-leveling and central backup applications. The present electrochemical energy storage systems are too costly to penetrate major new markets. Higher performance is required, and environmentally acceptable materials are preferred. Transformational changes in electrical energy storage science and technology are in great demand to allow higher and faster energy storage at lower costs, and longer lifetimes are necessary for major market enlargement. Most of these changes require new materials and/or innovative concepts, with demonstration of larger redox capacities that react more rapidly and reversibly with cations and/or anions.
Batteries are by far the most common form of storing electrical energy ranging from: standard every day lead-acid cells, exotic iron-silver batteries for submarines taught by Brown in U.S. Pat. No. 4,078,125, nickel-metal hydride (NiMH) batteries taught by Kitayama in U.S. Pat. No. 6,399,247 B1, metal-air cells taught in U.S. Pat. No. 3,977,901 (Buzzelli), to Isenberg in U.S. Pat. No. 4,054,729, and to the lithium-ion battery taught by Ohata in U.S. Pat. No. 7,396,612 B2. These latter metal-air, nickel-metal hydride and lithium-ion battery cells require liquid electrolyte systems.
Batteries range in size from button cells used in watches, to megawatt load leveling applications. They are, in general, efficient storage devices, with output energy typically exceeding 90% of input energy, except at the highest power densities. Rechargeable batteries have evolved over the years from lead-acid through nickel-cadmium and nickel-metal hydride (NiMH) to lithium-ion batteries. NiMH batteries were the initial workhorse for electronic devices such as computers and cell phones, but they have almost been completely displaced from that market by lithium-ion batteries because of the latter's higher energy storage capacity. Today, NiMH technology is the principal battery used in hybrid electric vehicles, but it is likely to be displaced by the higher power energy and now lower cost lithium batteries, if the latter's safety and lifetime can be improved. Of the advanced batteries, lithium-ion is the dominant power source for most rechargeable electronic devices.
What is needed is a dramatically new electrical energy storage device that can easily discharge and charge a high capacity of energy quickly and reversibly, as needed. What is also needed is a device that can operate for years without major maintenance. What is also needed is a device that does not need to operate on natural gas, hydrocarbon fuel or its reformed by-products such as H2. One possibility is a rechargeable oxide-ion battery (ROB), as set out application Ser. No. 12/695,386, filed on Jan. 28, 2010.
A ROB comprises a metal electrode, an oxide-ion conductive electrolyte, and a cathode. The metal electrode undergoes reduction-oxidation cycles during charge and discharge processes for energy storage. For example, in discharging mode, the metal is oxidized:yMe+x/2O2=MeyOx and is reduced in charging mode:MeyOx=x/2O2+yMe, where Me=metal.
We have found, that for energy storage application, oxide ion must be transported across the electrolyte between metal electrode and cathode to carry electrical charge. Therefore, the metal electrode must be properly sealed heimetically to prevent direct contact with oxygen-containing environment (for example, air). Otherwise, oxygen in air will directly consume the metal without involving charge transfer between electrodes, which will lead to self discharge. High-temperature sealing materials such as glasses and ceramic-glass composites in principle are good candidates for this purpose. However, reliability of high-temperature sealing materials remains questionable upon thermal cycle and long-term operation. Therefore, there is need to design ROB cells whose metal electrode is sealed solely by the cell electrolyte and interconnection without using additional materials for sealing purpose.